From corrosion resistance to discharge efficiency: the pivotal role of the CaMgSn phase in Mg–Sn–Ca anodes
摘要
In this study, comprehensively explored the impacts of Sn and Ca introduced at a constant mass ratio of 3:1 (0.6:0.2, 1.2:0.4, 2.4:0.8 wt%) on the microstructural features, discharge properties, and corrosion characteristics of ternary Mg–Sn–Ca alloys. Microstructural characterization outcomes demonstrate that solely a single CaMgSn intermetallic phase precipitates within all three fabricated alloys. The area fraction of the CaMgSn phase rises markedly from 1.66% to 6.18% as the addition level of alloying elements increases, while the average grain dimension of the alloys undergoes pronounced refinement from 24.20 μm to 11.39 μm concurrently. Electrochemical test results confirm that, as Sn and Ca contents increase, the corrosion potential of the alloys shifts in the negative direction, corrosion current density elevates, and corrosion rate increases drastically. The Mg–2.4Sn–0.8Ca alloy attains the maximum corrosion rate, reaching as high as 100.02 mm y⁻1. Galvanostatic discharge test results reveal that the Mg–2.4Sn–0.8Ca alloy delivers the highest discharge potential at all examined current densities, and exhibits superior discharge stability across all tested current densities except for 40 mA cm⁻2. Microstructural analysis after discharge shows that a compact, homogeneously distributed crack network forms on the Mg–2.4Sn–0.8Ca alloy surface following the discharge process, which promotes the timely shedding of discharge products and sustains uninterrupted contact between the fresh alloy surface and the electrolyte. Meanwhile, the uniform dispersion of the CaMgSn phase supplies plentiful electrochemically active sites, which markedly speeds up the anodic reaction kinetics. Among all investigated alloys, the Mg–2.4Sn–0.8Ca alloy presents outstanding application prospects as a high-efficiency anode material for Mg-air battery systems.